Eclipse Photography

The eclipse may be safely photographed provided that the above
precautions are followed. Almost any kind of camera with manual
controls can be used to capture this rare event. However, a lens
with a fairly long focal length is recommended to produce as large
an image of the Sun as possible. A standard 50 mm lens yields
a minuscule 0.5 mm image, while a 200 mm telephoto or zoom produces
a 1.9 mm image. A better choice would be one of the small, compact
catadioptic or mirror lenses that have become widely available
in the past ten years. The focal length of 500 mm is most common
among such mirror lenses and yields a solar image of 4.6 mm. With
one solar radius of corona on either side, an eclipse view during
totality will cover 9.2 mm. Adding a 2x tele-converter will
produce a 1000 mm focal length, which doubles the Sun's size to
9.2 mm. Focal lengths in excess of 1000 mm usually fall within
the realm of amateur telescopes. If full disk photography of partial
phases on 35 mm format is planned, the focal length of the optics
must not exceed 2600 mm. However, since most cameras don't show
the full extent of the image in their viewfinders, a more practical
limit is about 2000 mm. Longer focal lengths permit photography
of only a magnified portion of the Sun's disk. In order to photograph
the Sun's corona during totality, the focal length should be no
longer than 1500 mm to 1800 mm (for 35 mm equipment). However,
a focal length of 1000 mm requires less critical framing and can
capture some of the longer coronal streamers. For any particular
focal length, the diameter of the Sun's image is approximately
equal to the focal length divided by 109
(Table 25).

A mylar or glass solar filter must be used on the lens throughout
the partial phases for both photography and safe viewing. Such
filters are most easily obtained through manufacturers and dealers
listed in Sky & Telescope and Astronomy magazines
(see: Appendix 1). These filters typically attenuate the Sun's
visible and infrared energy by a factor of 100,000. However, the
actual filter factor and choice of ISO film speed will play critical
roles in determining the correct photographic exposure. A low
to medium speed film is recommended (ISO 50 to 100) since the
Sun gives off abundant light. The easiest method for determining
the correct exposure is accomplished by running a calibration
test on the uneclipsed Sun. Shoot a roll of film of the mid-day
Sun at a fixed aperture (f/8 to f/16) using every shutter speed
between 1/1000 and 1/4 second. After the film is developed, note
the best exposures and use them to photograph all the partial
phases. The Sun's surface brightness remains constant throughout
the eclipse, so no exposure compensation is necessary except for
the narrow crescent phases which may require two more stops due
to solar limb darkening. Bracketing by several stops may also
be necessary if haze or clouds interferes on eclipse day.

Certainly the most spectacular and awe inspiring phase of the
eclipse is totality. For a few brief minutes or seconds, the Sun's
pearly white corona, red prominences and chromosphere are visible.
The great challenge is to obtain a set of photographs which captures
some aspect of these fleeting phenomena. The most important point
to remember is that during the total phase, all solar filters
must be removed! The corona has a surface brightness a
million times fainter than the photosphere, so photographs of
the corona are made without a filter. Furthermore, it is completely
safe to view the totally eclipsed Sun directly with the naked
eye. No filters are needed and they will only hinder your view.
The average brightness of the corona varies inversely with the
distance from the Sun's limb. The inner corona is far brighter
than the outer corona. Thus, no one exposure can capture its the
full dynamic range. The best strategy is to choose one aperture
or f/number and bracket the exposures over a range of shutter
speeds (i.e. - 1/1000 down to 1 second). Rehearsing this sequence
is highly recommended since great excitement accompanies totality
and there is little time to think.

Exposure times for various combinations of film speeds (ISO),
apertures (f/number) and solar features (chromosphere, prominences,
inner, middle and outer corona) are summarized in
Table 26. The
table was developed from eclipse photographs made by Espenak as
well as from photographs published in Sky and Telescope.
To use the table, first select the ISO film speed in the upper
left column. Next, move to the right to the desired aperture or
f/number for the chosen ISO. The shutter speeds in that column
may be used as starting points for photographing various features
and phenomena tabulated in the 'Subject' column at the far left.
For example, to photograph prominences using ISO 100 at f/11,
the table recommends an exposure of 1/500. Alternatively, you
can calculate the recommended shutter speed using the 'Q' factors
tabulated along with the exposure formula at the bottom of
Table 26.
Keep in mind that these exposures are based on a clear sky
and a corona of average brightness. You should bracket your exposures
one or more stops to take into account the actual sky conditions
and the variable nature of these phenomena.

Another interesting way to photograph the eclipse is to record
its various phases all on one frame. This is accomplished by using
a stationary camera capable of making multiple exposures (check
the camera instruction manual). Since the Sun moves through the
sky at the rate of 15 degrees per hour, it slowly drifts through
the field of view of any camera equipped with a normal focal length
lens (i.e. - 35 to 50 mm). If the camera is oriented so that the
Sun drifts along the frame's diagonal, it will take over three
hours for the Sun to cross the field of a 50 mm lens. The proper
camera orientation can be determined through trial and error several
days before the eclipse. This will also insure that no trees or
buildings obscure the camera's view during the eclipse. The Sun
should be positioned along the eastern (left in the northern hemisphere)
edge or corner of the viewfinder shortly before the eclipse begins.
Exposures are then made throughout the eclipse at ~five minute
intervals. The camera must remain perfectly rigid during this
period and may be clamped to a wall or fence post since tripods
are easily bumped. If you're in the path of totality, you'll want
to remove the solar filter during the total phase and take a long
exposure (~1 second) in order to record the corona in your sequence.
The final photograph will consist of a string of Suns, each showing
a different phase of the eclipse.

Finally, an eclipse effect that is easily captured with point-and-shoot
or automatic cameras should not be overlooked. Use a kitchen sieve
or colander and allow its shadow to fall on a piece of white card-board
placed several feet away. The holes in the utensil act like pinhole
cameras and each one projects its own image of the Sun. The effect
can also be duplicated by forming a small aperture with one's
hands and watching the ground below. The pinhole camera effect
becomes more prominent with increasing eclipse magnitude. Virtually
any camera can be used to photograph the phenomenon, but automatic
cameras must have their flashes turned off since this would otherwise
obliterate the pinhole images.

For those who choose to photograph this eclipse from one of the
many cruise ships in the path, some special comments are in order.
Shipboard photography puts certain limits on the focal length
and shutter speeds that can be used. It's difficult to make specific
recommendations since it depends on the stability of the ship
as well as wave heights encountered on eclipse day. Certainly
telescopes with focal lengths of 1000 mm or more can be ruled
out since their small fields of view would require the ship to
remain virtually motionless during totality, and this is rather
unlikely even given calm seas. A 500 mm lens might be a safe upper
limit in focal length. Film choice could be determined on eclipse
day by viewing the Sun through the camera lens and noting the
image motion due to the rolling sea. If it's a calm day, you might
try an ISO 100 film. For rougher seas, ISO 400 or more might be
a better choice. Shutter speeds as slow as 1/8 or 1/4 may be tried
if the conditions warrant it. Otherwise, stick with a 1/15 or
1/30 and shoot a sequence through 1/1000 second. It might be good
insurance to bring a wider 200 mm lens just in case the seas are
rougher than expected. As worst case scenario, Espenak photographed
the 1984 total eclipse aboard a 95 foot yacht in seas of 3 feet.
He had to hold on with one hand and point his 350 mm lens with
the other! Even at that short focal length, it was difficult to
keep the Sun in the field. However, any of the major cruise ships
in the Caribbean will offer a far more stable platform than this.

For more information on eclipse photography, observations and
eye safety, see Further Reading
in the Bibliography.